In an elegant confluence of two of my central interests -- neuroimaging and the social determinants of health, the Chronicle of Higher Education reports on some fascinating research forthcoming in the journal Developmenmtal Science.
The PI is Martha Farah, who is a cognitive neuroscientist at Penn and is doing important work in neuroethics. (In fact, Farah is on the Executive Committee of the Neuroethics Society, and she has a fascinating paper in the new journal Neuroethics, edited by Neil Levy).
According to the article, the question Farah et al. set out to investigate is the extent of low socioeconomic status on neural structure.
She and her colleagues have investigated the issue by trying to tease out which aspects of poverty alter specific cognitive skills, such as memory, language, and the ability to delay gratification. The researchers studied a group of African-American children of low socioeconomic status, who had been tracked from birth through high-school graduation by Hallam Hurt, a pediatrician at Penn.
Over the years, Dr. Hurt's team had assessed the home environments of the children, monitoring how nurturing parents were, and how intellectually stimulating the homes were—for example, whether the children had access to books and visited museums.
Farah et al. reportedly found that cognitive skills were linked with particular features of the environment, such as how "intellectually stimulating" the home environment was.
To test why, the researchers did MRI scans of the children. They found that students raised in nurturing homes generally had bigger hippocampi, the portion of the brain associated with forming and retrieving memories. The discovery dovetails with previous research in rodents, which showed that rats raised in a stressful environment develop smaller hippocampi.
The article goes on to note that while prevailing opinion at the "annual meeting . . . of the American Association for the Advancement of Science" (where Farah et al. presented the finding) supported the notion that social conditions is a prime determinant in neural development, some cautioned that the extent of the correlation is unclear.
There is more in the article, including some interesting work on stress in children related to low socioeconomic status. As they say, go read the whole thing.
Work on early childhood development, including neural development, is important in SDOH research. The best evidence suggests that social and economic factors may act as a kind of trigger -- not a prime cause, but a trigger -- for a cascade of subsequent stimuli that correlate strongly with poor health outcomes (and poor education, as well, which is even more strongly correlated with poor health outcomes). The causal relationship here is both extremely complicated and quite murky, as it is not the case that deleterious social conditions in early childhood inevitably cause poor health in a linear sense. Nevertheless, the epidemiologic evidence seems to link such conditions in early childhood -- as far back as prenatal periods -- to just such a "cascade."
While it seems prudent to avoid commenting further on the significance of the observations regarding the size of the children's hippocampi until the study is available for review, the notion that early childhood development seems to be of great significance in protracted health measures is evidence-based. Such an evidence base may support greater allocation of resources to early childhood development programs as a means of enhancing population health. Indeed, some SDOH scholars urge just such investment as a public health policy.
Two further points. First, though this likely crosses the barely perceptible line I (vainly?) try to maintain between my professional life and this blog, I would like to again suggest that those interested in this issue should hasten to review the report prepared by my colleague, Dr. Winifred Hamilton, who heads the environmental health group at Baylor College of Medicine's Chronic Disease Prevention & Control Research Center, where I work. The report meticulously documents a staggering lead problem in Galveston, TX (where I attend graduate school). The report may be downloaded here.
Second, the possibility that chronic stress can exert strong influences on neural development is consonant with work (see Brunner & Marmot 2006) suggesting that stress may activate the neuroendocrine pathway in ways that seem to produce illness and poor health. Indeed, such a pathway is one of the most promising explanatory models for grounding how social and economic conditions may cause molecular changes.
In any case, it was exciting to see a convergence of two of my own central research interests, and I look forward to reading the study when it is published (I will post a follow-up with the link once it becomes available).
(h/t SDOH Listserv)
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